In coils for the electrical or electronic equipment, including inverter-related equipment, such as high-speed switching devices, inverter motors, transformers, and the like, insulated electric wires are used as a magnet wire. Examples of the insulated electric wires include an insulated electric wire (insulated wire) composed of a so-called enamel wire, an insulated wire having multi-covering layers including a layer composed of an enamel resin and a covering layer composed of another kind of resin other than the enamel resin, and the like.
In regard to coils for the electrical or electronic equipment, various techniques have been developed in order to immobilize the insulated wire (winding wire) or to enhance the insulation property. For example, Patent Literature 1 discloses a structure in which a rectangular conductor whose outer periphery is coated with an insulating coating is stacked on top of each other to form a laminate and a sheet-like base material provided thereon with a thermosetting resin adhesive layer formed using an epoxy resin composition is coated on the outer periphery of said laminate. Patent Literature 2 discloses a technique of disposing an insulating paper at coil housing grooves formed at a stator core of a rotating electrical machine, immobilizing the coil at the coil housing groove using a varnish, and thereby immobilizing the coil while providing insulation between the coil and the stator core.